In recent years, various vehicular systems and devices such as an air-conditioner, a radio, a CD/DVD player, a navigation system and the like are controlled by using a manual operation device, that is, a manual operation control unit having, for example, a rotary switch or the like. More practically, control information for setting temperature, for a selection of radio stations, for organizing a navigation route or the like is integrally displayed on a display unit, and a user, i.e., an occupant or a driver of the vehicle, is encouraged to control operation conditions of those systems and devices by, for example, a button in a touch panel on the display unit or the like.
However, the occupant of the vehicle is required to watch the operation conditions represented on the display unit very carefully in order to see the result of his/her control while being involved in, for example, a driving operation of the vehicle. In other words, arbitrary arrangement of the buttons and/or an indicator on the display unit may not be very easy to read in terms of readiness for control result recognition unless the occupant are familiar with the arrangement of the buttons and/or representation of the control result.
In view of the above-described problems, disclosure in Japanese Patent Document JP-A-2001-84475 describes a technique of “Haptics,” or a reaction force control technique in response to an operation of a control device and/or a situation of a control operation. This technique controls a manual operation of a control interface of various devices by providing a reaction force to the interface according to an operation position, an operation condition of the device. The disclosure of the above document also describes an application of a thrusting force in addition to the reaction force.
More practically, the application of the reaction force works in the following manner. That is, the haptics technique applies resistance to a volume-up control operation of, for example, a CD/DVD player by providing the reaction force when the user operates a manual operation volume switch on the player, and a volume-down control operation of the manual operation volume switch is assisted by a provision of the thrusting force to facilitate rotation of the volume switch in a volume-down direction. In this manner, a sudden burst of large sound is prevented when the occupant controls the volume switch toward a greater volume, or a sharp decrease of large sound is possible for providing a conversational sound condition in the vehicle based on the thrusting force for the volume down control.
However, the reaction force and/or the thrusting force may not always provide an appropriate assist for the occupant or the driver to suitably operate the volume switch or the like. For example, the reaction force having a less-than-expected resisting force strength may allow the user to drive a manual operation control unit excessively to select an intended function. Further, the reaction force may induce or trigger an unintended invocation of assigned function when the occupant unconsciously operates the manual operation control unit besides being involved in the driving operation. On the other hand, the reaction force may restrict the manual operation of the occupant who is too weak to resist the reaction force applied thereto. The reaction force having a more-than-expected strength may distract the attention of the occupant away from, for example, the driving operation of the vehicle.
Based on the reasoning described above, the manual operation control unit may preferably apply the reaction force to the manual operation of the occupant or the like in an adjustable manner. Disclosure in Japanese Patent Document JP-A-2003-260949 describes the adjustment method of the reaction force for the Haptics devices. This technique defines plural characteristic points and connecting function for forming a force pattern applied to the manual operation control unit in order to reduce the number of settings for force pattern definition. In this manner, the manual operation control unit which usually requires a detailed reaction force definition for every operation position in an entire control area can be suitably operated by the manual operation of the user by defining only a few control values for characteristic points.
However, the control values for the characteristic points can only be discovered based on a sufficient knowledge of the characteristic points and the connecting function accompanied by a knack of settings. Further, the connecting function may deceive an intuition of the user of the manual operation control unit in terms of the strength of the reaction force between the characteristic points, thereby causing difficulty for reaction force adjustment by the user.